The invention relates generally to coolant circulation systems for internal-combustion engines, and more specifically to coolant circulation systems for use in motorcycle engines.
One example of a fluid-moving device or pump for use with an internal-combustion engine is disclosed in U.S. Pat. No. 4,436,067. Pumps of this type generally include a housing, a cover, and an impeller assembly arranged between the housing and the cover. The impeller assembly generally conveys a coolant from a low-pressure side of the pump to a high-pressure side of the pump. The coolant then travels from the high-pressure side throughout the engine to cool various elements within the engine before returning to the low-pressure side and being recycled through the pump.
In many conventional pumps, there is a tendency for at least a portion of the coolant to leak from the high-pressure side to the low-pressure side, thereby reducing the efficiency of the pump. It is therefore desirable to reduce or eliminate leakage of coolant from the high-pressure side to the low-pressure side of the pump. Also, the pump should be relatively simple to manufacture and assemble and should include relatively few parts.
The present invention provides an apparatus for cooling internal-combustion engines by cycling a coolant through the engine to cool engine components during operation and startup of the engine. In the present invention a pump is preferably mounted relatively close to the crankcase and is selectively in fluid communication with a coolant loop, which preferably extends throughout the engine and a radiator.
In particular, the pump includes a housing and a cover sealingly coupled together with a flange arranged between the housing and the cover. The cover and the flange define a first or low-pressure cavity. The housing and the flange define a second or high-pressure cavity. A central opening, extending through the flange, connects the first and the second cavities. An impeller assembly, which includes an impeller shaft, extends through an aperture in the housing into the high-pressure cavity for rotation about a longitudinal axis. Fasteners such as bolts, screws, adhesives, clasps, and the like preferably hold the cover, the flange, and the housing together. Also, fasteners preferably hold the pump on the engine.
The impeller assembly is preferably mounted relatively close to the flange to draw coolant from the first cavity through the central opening in the flange and into the second cavity. To improve the efficiency of the pump and to prevent coolant from leaking past the impeller assembly from the second cavity to the first cavity, the impeller assembly is positioned immediately adjacent the central opening, with only enough clearance between the flange and the impeller assembly to allow the impeller assembly to rotate about the longitudinal axis without contacting the flange. In this manner, the impeller assembly can draw coolant from the first cavity to the second cavity and can simultaneously prevent or limit coolant from leaking through the central opening and from the second cavity to the first cavity. Additionally, a seal is preferably maintained between the cover and the flange so that coolant cannot leak out of the second cavity to the outside of the pump.
In a second aspect of the present invention, the impeller assembly has a relatively circular hub. An aperture preferably extends through the hub for receiving the impeller shaft. A front face of the impeller assembly is adjacent the central opening. Preferably, arcuately shaped blades are coupled to the front face of the impeller assembly and extend radially from the hub, curving toward the periphery of the front face. The blades are preferably contoured to draw the coolant from the first cavity through the flange and into the second cavity. Preferably, rotation of the arcuately shaped blades within the second cavity creates an area of suction, which draws coolant from the first cavity into the second cavity. Also, the arcuately shaped blades preferably prevent or limit coolant from leaking past the impeller assembly from the second cavity to the first cavity.
Preferably, a nozzle is coupled to the flange. The nozzle preferably has a first end in fluid communication with the first cavity and a second end in fluid communication with the second cavity. The second end of the nozzle preferably has a diameter slightly larger than the diameter of the front face of the impeller assembly so that the front face of the impeller assembly can extend into the second end of the nozzle. The nozzle is preferably a converging-diverging nozzle, with relatively wide openings at the first and second ends, tapering to a throat positioned between the first and second ends.
In operation, coolant preferably enters the pump through one or more coolant intake ducts, which are preferably in fluid communication with the coolant loop and/or the radiator. Preferably, rotation of the impeller assembly within the second cavity causes the pressure in the second cavity to be relatively higher than the pressure in the first cavity. Additionally, the pressure in the coolant loop, extending throughout the engine, is preferably relatively higher than the pressure in the first cavity. This difference in pressure causes coolant to be drawn from the coolant loop and/or the radiator into the first cavity through the coolant intake ducts. Next, the impeller assembly draws the coolant from the relatively low-pressure first cavity, through the opening in the flange.
Preferably, the impeller assembly draws coolant into the nozzle through the first end of the nozzle. The coolant travels through the throat, is directed through the second end of the nozzle onto the arcuately shaped impeller blades, and is flung off of the blades into the second cavity. In this manner, the nozzle and the impeller assembly preferably minimize turbulence and maintain relatively laminar flow through the nozzle. Additionally, the relatively close contact between the second end of the nozzle and the front face of the impeller assembly limits the coolant from leaking through the central opening from the second cavity to the first cavity, thereby improving the efficiency of the pump. Also, as coolant passes through the throat of the nozzle, the pressure and/or the flow rate of the coolant is increased, thereby further preventing or limiting coolant from leaking back through the nozzle from the second cavity to the first cavity.
In another aspect of the present invention, the arcuately shaped blades draw the coolant from the first cavity along a path, which is substantially parallel to the longitudinal axis. The arcuately shaped blades then force the coolant into the second cavity along a path extending radially away from the longitudinal axis.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings.